The What

Ever been confronted by a Spinning Pinwheel of Death on launch of SuperDuper! on Snow Leopard and, while waiting for it to stop doing that, raised your hands to the sky and cursed me and the ground I walk on?

Hey, me too (without the self-cursing—kids, remember, if you curse yourself you'll grow hair on your soul)! But (and here's the important part) it's not unique to SuperDuper!. You'll also see this when you do a File > Open, File > Save As, and many other actions. It's not just a delay due to drive spin-up, and there's a fix!

The Why

I can't pretend to totally understand why this happens, so please don't ask, but it seems that the dyld cache (if you don't know what that is, read it as "stuff deep inside OS X") gets in some sort of weird state, and that state is often seen, up in userland, as these annoying, inexplicable SPOD delays.

Might be best to think "damnable munchkins" is the real reason why. Or circuit ants. Or blame the iPhone 4's antenna: it's Mark Papermaster: he's taking the blame for everything else and, at this point, probably wouldn't mind.

The First Fix (for Users Uncomfortable with Terminal)

The easiest way to fix this is to power off your Mac, hold down the Shift key, keep it down and power back on. Keep Shift down all the way to the desktop. This starts your Mac, more slowly, in Safe Boot, which automatically rebuilds this cache (among other things).

When you're totally logged in and running, try running SuperDuper! or your other app that was slow with File > Open. You'll note that it's quite fast.